The group of 10 departed players combined to start 107 games in 2014 and play 6,355 snaps. Those figures roughly mirror the exodus after the 2010 season when the 49ers lost 11 players who had made at least one start. That group combined to start 114 games in 2010 and play 6,295 snaps. …

Dr. Vernon Williams, a neurologist and the founding director of the Kerlan-Jobe Center for Sports Neurology in Los Angeles, serves as a concussion consultant to a host of professional teams, colleges and high schools. …